The melt strength is a measure of the suitability of a polymer or of a polymer mixture for extrusion blow moulding. A measurement is made of the time t2 required for the parison to drop by a height of 25 cm and the time tl required by the parison to drop by a height of 50 cm; the melt strength is the ratio t1/t2. If the polymer or polymer mixture is suitable for the blow moulding of large parts then a ratio close to 2 is found. If it is not close to 2, on the other hand, for example if it is 1.4, this value indicates flow of the parison under its own weight (quickening of the rate of descent) and hence poor suitability for extrusion blow moulding.